Sample tap apparatus with pressure sensitive cap

ABSTRACT

A tap to a process fluid line includes a pressure sensitive cap. The force necessary to remove the cap on the tap is directly proportional to the pressure buildup inside the cap so that an operator can take safety measures before removing the cap. The tap includes a base having a first set of reusable threads thereon and a cap having a second set of reusable threads therein which engage with the first set of threads on the base. A hollow fill tube communicates fluid from the process fluid line through a ball valve to a sample bottle when the cap is removed. The resistance provided by the reusable threads is linear and consistent throughout the entire threading and unthreading procedure. In this manner the force necessary to remove the cap is proportional to the pressure buildup inside of the cap. A helical spring is attachable by an anchor to the fill tube and can be employed to steady the mouth of the sample bottle as it is filled by the fill tube. The invention helps to prevent industrial accidents by minimizing the hazard of sample fluid spills and by warning the operator of the buildup of dangerous pressure inside the cap prior to its removal.

This application is a continuation of application Ser. No. 08/379,187,filed Jan. 27, 1995, now U.S. Pat. No. 5,575,317, which issued on Aug.14, 1996.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a sampling tap apparatus in which a samplebottle is filled through a tap which includes a base and a pressuresensitive removable cap.

2. Description of Related Art

There are a number of known prior art approaches for tapping a fluidline. For example, a simple plug could be employed, but plugs tend towear out rapidly and can be messy to use. A plug would pose a majorproblem if the materials being sampled were environmentally dangerous.

A second option might be to employ a second valve in a fluid sampleline. Valves, however, also have the tendency to wear out and frequentlyget stuck in either the open or closed position if the materialsemployed are viscous.

One other possibility would be that if a flanged valve were used, ablind flange could be used to cap or seal off the outlet of the valvedownstream from the process side of the system. A blind flange, however,would be somewhat impractical for a typical sampling application becausethere are generally four bolts that would have to be dealt with in orderto remove or install a flange.

There are other problems with prior art approaches such as describedabove. If a 1/4" valve and a 1/4" pipe plug were placed together theymight meet the requirements set out in the U.S. Clean Air Act (CAA).However, it would be difficult to install the device and then to removethe 1/4" pipe plug from the valve each and every time the sample had tobe taken. Conversely, if two valves were used in series, it would stillbe necessary to add some sort of tube or pipe nipple that would directthe fluid flow into the sample bottle and the cost of that wouldprobably exceed the cost of the present invention.

In addition to the foregoing, none of the prior art devices describedabove are especially responsive to pressure buildup inside the sampleline. In other words, the effort to remove a plug or turn a valveaccording to the prior art techniques would be relatively independent ofthe pressure in the sample line. Accordingly, the operator would have nowarning of potential dangerous pressure buildup.

In summary, the prior art does not appear to teach or suggest aninexpensive sample tap apparatus which includes a cap having reusablethreads and which is sensitive to pressure buildup in the sample pipe.

SUMMARY OF THE INVENTION

Briefly described, the invention comprises a sampling tap apparatus inwhich the force necessary to remove the cap is proportional to thebuildup of pressure inside of the tap. A manually operated valve isconnected to a process line at one end and to the sample tap apparatusat the other. The base of the sample tap apparatus includes a fill tubewhich communicates with the control valve at one end and selectivelywith a sample bottle at the other. In an alternative embodiment, ahelical spring shaped guide is attached to the fill tube and serves tohelp hold the mouth of the sample bottle in position when it is beingfilled.

A reusable cap includes internal threads that mate with external threadson the base. The threads are linear in the sense that the distancebetween flights remains constant from beginning to end. In that way thethreads never bind and the cap is always reusable. In addition, and mostimportantly, the pressure necessary to unscrew the cap is constantthroughout the threading and unthreading operation so that the operatoris aware of any pressure buildup inside of the sample tap apparatus.This can be very critical if pressure inside the sample apparatus hasbuilt up to dangerous levels. An alternative embodiment of the capincludes a cavity having a resilient plug therein for sealing the openend of the fill tube and preventing unnecessary leakage. A securitycable attaches the sample fill line to the reusable cap so that the capdoes not become lost or damaged.

These and other features of the invention may be more fully understoodby reference to the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the sample tap apparatus according to the preferredembodiment of the invention in its closed state as connected to aprocess line.

FIG. 2 illustrates the first step in the sampling process in which thesample cap has been removed and a sample bottle is about to be placed inposition under the fill tube.

FIG. 3 illustrates a sample bottle being filled by a sample tapapparatus according to the preferred embodiment of the invention.

FIG. 4 is a cross-sectional view of an alternative embodiment of theinvention in which the cap is illustrated in its closed, engagedposition and in which the fill tube includes a helical guide spring forguiding the mouth of the bottle into position under the fill tube.

FIG. 5 illustrates the alternative embodiment of the present inventionas illustrated in FIG. 4 when the apparatus is employed to fill a samplebottle and the helical spring holds the mouth of the bottle in positionunder the fill tube.

DETAILED DESCRIPTION OF THE INVENTION

During the course of this description like numbers will be used toidentify like elements according to the different views that illustratethe invention.

The sample tap apparatus 10 according to the preferred embodiment of theinvention is illustrated in its closed state in FIG. 1. Sample tapapparatus 10 includes a reusable cap 12 that includes internal threadswhich engage with a second set of threads on a base 14. Security cable16 connects cap 12 to the threaded connector 18 in the base 14 toprevent the cap 12 from becoming lost or damaged. Threaded connector 18connects base 14 to the downstream end of valve 20. Valve 20 isconnected at the other end thereof to a process line 24. A handle 22controls the opening and closing of valve 20 in the conventional manner.Knurling hash marks 26 on cap 12 make it possible for an operator tomanually thread or unthread the cap 12. Knurling 26 also makes itpossible for the operator to have a better "feel" of the pressurebuildup, if any, inside the sample tap apparatus 10. Wrench flats 28 onbase 14 make it possible for an installer to easily connect the sampletap apparatus 10 to valve 20.

FIG. 2 illustrates the manner in which the cap 12 is readily removedfrom the base 14 prior to the filling of a sample bottle 32. Samplebottle 32 includes a mouth 30 that fits over the fill tube 34 of thesample tap apparatus 10. Typically, an operator would remove the cap 12using one hand 36 while holding the sample bottle 32 in the other hand56. As shown in FIG. 2, the cap 12 has an inside 40 which includesthreads 42 which mate with threads 38 on base 14. According to thepreferred embodiment of FIGS. 1-3, the fill tube 34 comes close to, butdoes not touch, the bottom of cap cavity 40 when the cap 12 is fullyscrewed onto base 14. Threads 42 include a pair of relatively flat,inwardly tapered, sidewalls separated by a third flat exterior surface.Unlike conventional threads, however, threads 42 are linear, that is tosay, not generally tapered along their length. Conventional pipe threadsare tapered in such a way that increased screw down pressure causes thetwo threaded surfaces to mate more snugly. In contrast, because threads42 are linear along their length and because they mate with threads 38,which likewise are linear along their length, the mating of threads 38and 42 do not experience nonlinear resistance as the threads areprogressively engaged. This has several advantages. First, the threadsare indefinitely reusable because there is no significant wear. Second,and most importantly, any pressure buildup on the inside 40 of cap 12can be detected by the hand 36 of the operator during the cap removalprocess. Pressure inside of cap 40 builds up and exerts a force onthreads 42 which is substantially directly proportional to the actualpressure inside of the sample tap apparatus 10. Therefore, the operatorknows in advance if there might be any danger from an explosion due tothe pressure buildup in the sample tap apparatus 10. The preferreddimensions and characteristics of threads 38 and 42 are those thatconform to ISO standards 2904 (and ISO 2903) for tolerances. Theserelatively unique threads are sometimes used on machine tools, such asindustrial lathes, where it is desirable to remove the work piece fromthe machine.

FIG. 3 illustrates the manner in which a sample bottle 32 is filled oncethe cap 12 is removed as previously described with reference to FIG. 2.The mouth 30 of sample bottle 32 is placed in the vicinity of the openend of the fill tube 34. A stream of fluid 44 passes from the processline 24 through valve 20, threaded connector 18, base 14 and fill tube34, into the interior of the sample bottle 32. While the foregoing issatisfactory for many applications, it has been found that the mouth 30of the sample bottle 32 has to be kept in alignment with the fill tube34 otherwise the sample stream 44 may splash outside of the samplebottle 32 and injure the operator or contaminate the environment.

In order to minimize operator harm and environmental damage, thepreferred embodiment of the sample tap apparatus 10 as illustrated inFIGS. 1-3 can be supplied with a helical guide spring 50 and a resilientseal plug 48 as illustrated in the alternative embodiment shown in FIGS.4 and 5. The preferred embodiment 10 shown in FIGS. 1-3 includes a filltube 34 that extends down to, but does not touch, the bottom of thecavity 40 in cap 12. This permits pressure to be distributed effectivelyover the entire interior area 40 of cap 12. The alternative embodimentof FIGS. 4-5 includes an alternative plug 48 that may be used to sealtube 34 with respect to cap 12. FIG. 4 is a cross-section of thealternative embodiment of the invention showing the cap 12 in its closedand fully engaged position with respect to base 14. The open end of filltube 34 contacts and engages resilient plug 48 located in an internalcavity 46 in cap 12. Plug 48 helps to seal off the open end of fill tube34 to prevent leakage of sample fluid 44 and the buildup of pressurewithin the interior 40 of cap 12. An O-ring seal or gasket 52 furtherhelps to prevent the escape of fluid 44 from the interior cavity 40 ofcap 12 to the outside environment. In order to hold the mouth 30 of asample bottle 32 steady with respect to fill tube 34, the sample tapapparatus 10 is provided with a helical guide spring 50 which isattached at its narrow end by a circular anchor 54 to the upstream endof the fill tube 34. FIG. 5 illustrates how the helical guide spring 50operates with respect to the mouth 30 of a sample bottle 32. Becauseguide spring 50 is helical in shape, it guides the mouth of bottle 30like a funnel over the fill tube 34. The flexibility of spring 50 alsopermits the operator to hold the sample bottle 32 at a variety ofdifferent angles without the bottle becoming misaligned with respect tofill tube 34. Also, spring 50 tends to grab the mouth 30 of bottle 32and thereby assists the operator in supporting the weight of the samplebottle 32.

It should be clear from the foregoing that the sample tap apparatus 10according to the preferred and alternative embodiments of the inventionhas certain advantages over prior art approaches.

First, the sample tap apparatus 10 is relatively inexpensive, completelyreusable, and easy to clean and maintain.

Second, because the threads 38 and 42 are linear, the pressure requiredby an operator to remove cap 12 is substantially directly proportionalto the buildup of pressure within the interior 40 of the sample tapapparatus 10. Therefore, the operator has advance warning that thepressure inside the sample tap apparatus 10 may be at dangerous levelsand can take appropriate actions to avoid injury or environmental harm.The knurling 26 on cap 12 further enhances the tactile ability of theoperator to sense the buildup of dangerous pressures within the sampletap apparatus 10.

Third, in order to further assure safety, an alternative helical guidespring 50 is provided to hold the mouth 30 of a sample bottle 32 inproper alignment with regard to fill tube 34 thereby preventingaccidental spills.

Fourth, another alternative embodiment calls for a resilient plug 48 toseal the end of fill tube 34 to help prevent leaks inside of cap 12.

While the invention has been described with reference to the preferredembodiment thereof, it would be appreciated by those of ordinary skillin the art that modifications can be made to the structure of theinvention without departing from the spirit and scope of the inventionas a whole.

We claim:
 1. A pressure sensitive tap apparatus for sampling a source ofenvironmentally dangerous and harmful fluids, said apparatuscomprising:a base connectable to said fluid source, said base having aninterior and an exterior, said base also having a first set of threadson said exterior thereof; a first fill tube having a first and a secondend and a channel therethrough wherein said first end is attached tosaid base, is located closest to said fluid source and communicates withsaid fluid source, and said second end is located furthest from saidfluid source and extends beyond said first set of threads, and furtherwherein said fill tube is substantially vertical with respect togravity; a pressure sensitive cap having an outside surface, a centralaxis and an interior cavity, said interior cavity including a second setof parallel threads thereon equidistant from said central axis, saidsecond set of threads having a cross-section which includes a first anda second sidewall lying in first and second planes, respectively,tapered in towards said central axis and a third surface lying betweensaid first and second sidewalls in a third plane different from saidplanes of said first and second sidewalls; and, annular seal meanslocated in said interior cavity of said cap for contacting said base andfor preventing fluid from escaping from said interior cavity of said capwhen said cap is screwed onto said base,wherein the resistance providedby said first set of threads acting against said second set of threadsas said cap is screwed onto and off of said base is substantially linearat all times so that the force necessary to unscrew said cap issubstantially proportional to the pressure buildup inside of saidinterior cavity of said cap and wherein a vessel may be filled by saidfill tube when said cap is removed.